Details

Autor(en) / Beteiligte

• Joe-Wong, Claresta
• Brown, Gordon E.
• Maher, Kate

Titel

Kinetics and Products of Chromium(VI) Reduction by Iron(II/III)-Bearing Clay Minerals

Ist Teil von

• Environmental science & technology, 2017-09, Vol.51 (17), p.9817-9825

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2017

Quelle

MEDLINE

Beschreibungen/Notizen

• Hexavalent chromium is a water-soluble pollutant, the mobility of which can be controlled by reduction of Cr­(VI) to less soluble, environmentally benign Cr­(III). Iron­(II/III)-bearing clay minerals are widespread potential reductants of Cr­(VI), but the kinetics and pathways of Cr­(VI) reduction by such clay minerals are poorly understood. We reacted aqueous Cr­(VI) with two abiotically reduced clay minerals: an Fe-poor montmorillonite and an Fe-rich nontronite. The effects of ionic strength, pH, total Fe content, and the fraction of reduced structural Fe­(II) [Fe­(II)/Fe­(total)] were examined. The last variable had the largest effect on Cr­(VI) reduction kinetics: for both clay minerals, the rate constant of Cr­(VI) reduction varies by more than 3 orders of magnitude with Fe­(II)/Fe­(total) and is described by a linear free energy relationship. Under all conditions examined, Cr and Fe K-edge X-ray absorption near-edge structure spectra show that the main Cr-bearing product is a Cr­(III)-hydroxide and that Fe remains in the clay structure after reacting with Cr­(VI). This study helps to quantify our understanding of the kinetics of Cr­(VI) reduction by Fe­(II/III)-bearing clay minerals and may improve predictions of Cr­(VI) behavior in subsurface environments.